Method of conditioning air



Oct. 29, 1957 A. B. NEWTON METHOD OF CONDITIONING AIR Filed Dec. 10, 1954 INVENTOR.' /ZQMM I United States Patent METHOD OF CONDITIONING AIR Alwin B. Newton, Wichita, Kans., assignor to The Coleman Company, Inc., Wichita, Kans., a corporation of Kansas Application December 10, 1954, Serial No. 474,551

6 Claims. (Cl. 18S-114.2)

This invention relates to a method of conditioning air and more particularly, to a method of conditioning air to any desired latent-sensible temperature. The method of this invention has particular utility for airconditioning houses having gas-tired or oil-fired circulating air heating systems. It also has other uses and applications.

It is a general object of this invention to provide an efhcient and economical method of conditioning7 air adapted for use in conjunction with circulating air heating systems, especially a gas-fired or oil-fired circulating air heating system. A more specic object is to provide a method for adjusting the sensible-latent heat ratio of the conditioning process, and more particularly to provide a method for reducing the sensible temperature and maintaining it at a comfortable level, say 70 to 80 F., while also conditioning the air to a comfortable relative humidity, say 40 to 60% relative humidity. Still another object is to provide a method of the character described which does not require the use of yrefrigeran'ts or refrigeration, and instead can be operated by using water as the coolant, the temperature of which is controlled by usual outdoor wet bulb temperatures. Still another object is to provide a method of the character described which is adapted for continuous operation on the basis of a repeated cycle, being fully automatic, and requiring no special attention. Further objects and advantages will appear as the specication proceeds.

The method of this invention is diagrammatically illustrated in the attached drawing. lThis-drawing will subsev duce still further the sensible heat content of the `air whileincreasing its content of water vapor. As indicated,

- the Amethod is carried out in two stages, that is, the drying t kand heat removal steps are repeated at least twice before `thethurnidiication step.

I -Various.,adsorbents for water vapor can b e'used for the dehumidiiication of the air. ,Silica gel ingranular *.form, however, is the preferred adsorbent for this purtpvose, Y ln the rst step of `thevprocess the air to be conditioned is passed over `or through silica-gel or other Agranular adsorbent for `Water vapor. It will lbe-understood, of course, that the adsorbent material should be employed in a state which favors .the` adsorptionof water vapor, kthat is, in a relatively dry or, unsaturated state.

VThe removal of water vaporfrom the air bycontacting the air with the adsorbentwill result in asubstantial inincreasewin the sensible heat content of gthe air., thereby converting the latent heat o f `the water vapor into sensiheat ofithe air and adsorbent bed. As .a next step, n theV demoistured air of increased sensibleY heat content to an indirect heat exchange with water at a lower temperature than the air, to remove sensible heat from the air. This step reduces the total heat content of the air. The demoisturing and sensible heat removal steps are then repeated. Speciiically, the air of reduced sensible heat content is again contacted with a'silica gel adsorbent or other adsorbent for water vapor to reduce still further the water vapor content of the air while again increasing its sensible heat content, and thereafter the air is subjected to a second indirect heat exchange with water at a lower temperature than the air to remove sensible heat from the air. Further drying and sensible heat removal cycles can be employed if desired without departing from the present invention, although they will usually not be necessary.

The cooled demoisturized air obtained as described above is then preferably subjected to an adiabatic humidiiication by passing the air or a portion of the air through water sprays until the air or portion thereof is substantially saturated with water vapor, thereby reducing its temperature to the lowest temperature obtainable by adiabatic humidication. In other words, the air is contacted with liquid water to reduce still further its sensible heat content while increasing its content of water vapor. Since it would be undesirable for most airconditioning purposes to employ air which is saturated with water vapor, it will usually be preferable to subject only a portion of the air to adiabatic humidication, and then to mix this portion with the rest of the air, thereby obtaining air at a predetermined moisture content and sensible heat content within the range for human comfort.

An embodiment of the present invention is illustrated somewhat diagrammatically in the accompanying drawing. In this drawing, 1t) designates a blower which supplies return air to dryers 11 and 12, which contain the silica gel in granular form. The return air passing over the adsorbent in dryers 11 and 12 gives up part of its moisture content to the adsorbent while increasing the sensible heat content of the air. This is substantially adiabatic drying, although the web bulb temperature does not re'- main completely constant because some heat of adsorption slightly increases the normal adiabatic change.

The air discharged from dryers 11 and 12 is passed through a heat exchanger 1.3 where it is subjected to indirect heat exchange with water at a lower temperature vThis heat exchange step reduces the total heat of the air While leaving its moisture content unchanged. The air discharged from heat exchanger 13 is passed through a second pair of dryers 14 and 15, which also contain silica gel granules, and for the function of further reducing the moisture content of the air while again increasing its sensible heat content. The heat exchange step is also repeated by passing the air discharged from dryers 14 and 15 through a second heat exchanger 16 constructed like heat exchanger 134. This results in a reduction Vof the total heat content of the air, and prepares it for adiabatic humidiiication in water sprayer 17.

. Preferably, as illustrated in the drawing, a by-pass 18 is provided around water sprayer 17 for by-passing a selected portion of the air discharged from heat exchanger 16. By controlling the relative proportion of the air diverted through by-pass 18, it is possible to control the iinai conditioned air to the desired range of temperatures and relative humidities for human comfort. The portion of the air passing through water sprayer 17 is brought into direct contact with the liquid water in the sprays, causing the water to evaporate and increase the moisturercontent of the air. Preferably, this humidiiication is carried out in such a way that the air discharged from water sprayer 17 is substantially saturated. The air discharged from water sprayer i7 is then mixed With the by-pass air to provide the conditioned air.

A gas burner I9 is also shown on the drawing. The dotted lines Vextending from gas burner 19 to dryers 11 f and 14 are intended to indicate that heated gases from burner 19 can be employed to regenerate the granular adsorbent contained in the dryers. ln this way the adsorbent can be heated and dried, so that it can be reused. With the arrangementillustrated in the drawing, it will Vbe understood that the adsorbent should be periodically regenerated, preferably while no air is being passed through the dryers.

The drawing further shows an air cooling unit 20 pro- .l vided with a motor-driven blower 2l and spray heads 22 which are connected to the water cooling coils in heat sump 26 and returned to heat exchangers 13 and 1.4 by

` means of pump 27.

Instead of a cooling tower arrangement other sources of cool water can be used, such as a well, lake, etc.

In practicing the method of this invention for airconditioning homes, the return air may have a temperature ranging from 70 to 85 F. and a relative humidity of from 30 to 60%. Under these conditions the process can be carried out employing cooling water in the heat exchangers at any available temperature from 55 to 85 F.

Further, by the two drying or dehumidification steps described above, the aircan berrendered substantially free of water, andv can be given a relative humidity of less than Y 10%.l By way of speciiic example of the method, the

following can be set out:

Return air at 80 dry bulb and 67 wet bulb (50% jrelative humidity) is contacted with silica gel granules until its dry bulb temperature is increased-to 10S and its relative humidity to around 10%.1 The high sensible heat air is Athen passed throughV a heat exchanger having circulating water at 80, which reduces the dry bulb ternperature of the air to 85 with a lowerV latent heat content of 60 wet bulb' (about 22% relative humidity). ln the second stage of the drying cycle, the partially demoisturized air is again contacted with silica gel granules until it is substantially tree of water, the sensible heat to 108 dry bulb, the relative humidity being about 3%. A second stage heat exchange with Water at 80 reduces this high sensible heat air to 85 dry bulb Aand 53 wet bulb (relative humidity about 5%). This dry air is then divided into two streams, one of which is passed through a water sprayerV in which it is adiabatically humidied to the saturation point reaching a dry bulb temperature of about 53, and the other stream is by-passed around .the yvater sprayerso that the temperature and moisture content of this portion of the air remains substantially unchanged. The cooled saturated air is then mixed with the by-passed air in the proportions desired to produce conditioned air having a dry bulb temperature of 56 to 80 and a relative humidity of from 40 to 60%.

' While in the foregoing specification this invention has been described in relation to a specitic embodiment thereof and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to other embodiments and that many of the details set forth herein can be I varied widely without departing from the basic concepts of the invention. l

vl claim: 'lQln the treatment of air for humanicomfort, the

'lmeth'od'of conditioning water-vapor containing air characterized by the steps of contacting the air to be conditioned with an adsorbent for water vapor to reduce the Water vapor content of the air while increasing its sensible heat content, removing sensible heat from the air, again contacting the air with an adsorbent for water vapor, thereafter again removing sensible heat from the air, then converting liquid water into water vapor by contacting the liquid Water with part of the air to reduce still further the sensible heat content of the air while increasing its content of water vapor, and mixing portions of the air of increased water content with portions of the rest of said air.

2. The method of conditioning air containing Water vapor, characterized by the steps of contacting the air to be conditioned with an adsorbent for water Vapor to reduce the water vapor content of the air while increasing its sensible heat content, removing sensible heat from the air, again contacting the air with an adsorbent for water vapor, thereafter again removing sensible heat fromthe air, then humidifying only a portion of the air by contacting it with liquid water'to` reduce still further the sensible Y heat content of this portion of the air while increasing its vapor adsorbing condition to still further reduce the water vapor content of the air and at the same time increase its sensible heat content, then again removing sensible heat from therair by subjecting itto' an indirect heat exchange with water at a lower temperature than the air, then passing only a portion ofthe air through Vwater sprays to reduce still further the sensible heat content of the air while increasing its content of water vapor, and then mixing said portion of increased water content with the rest of the air from said second-mentioned sensible heat removal step. r

' 4. The method of conditioning air for human comfort, comprising bringing air`at a dry bulb temperature of from 70 to 85 F. and at a relative humidity of from 30 to 60% into contact with granular silica gel in a Water vapor adsorbing condition' to reduce the water vapor content of Vthe air While increasing its dry bulb temperature .to 4above-90 F., next subjecting said air to an indirect heat exchange with water having a temperature of from 55 to 85 F. to reduce the` dry bulb temperature of the air, again passing said air over granular silica gel in a water vaporadsorbing conditionr to still further reduce the Water vapor content of the air and at the same time increase its sensible heat content, then again subjecting said air to .anindirectheat exchange with water having a temperature 'of from 55 to 85 F. to reduce the dry bulb temperature ofV the air, vnally subjecting only a portion ofthev air to an adiabatic humidiiication stage until said air Portion is substantially saturated with water i vapor and has its dry bulb ,temperature reduced still further, while vby-passing-theY rest of said air around said humidie'ation stage, and then mixing portions of said humiditled-andby-passed air with each other.

5. flhe method ofconditioning air for human comfort, comprising contacting air containing water vapor with k an adsorbent -for water vapor to. reduce the water vapor content ofthe air vkwhile increasing its sensiblehe'at content, remov'ing sensible heat from the air by subjecting said air to an indirect -heat exchange with water maintained atapproximately the outdoor Wet bulb air temperature, again'contactingthe airjwith an adsorbent for water vapor, thereafter again removing sensible heat from the with water maintained at approximately the outdoor wet bulb air temperature, then passing only a portion of the air through water sprays to reduce still further the sensible heat content of the air while increasing its content of water vapor, while by-passing the rest of said air around said water sprays, and then mixing portions of said bypassed air portions of said -air of increased water content.

6. In the treatment of air for human comfort, the method of conditioning water-vapor containing air, comprising passing the air to be conditioned over granular silica gel in a water vapor adsorbing condition to reduce the water vapor content of the air while increasing its sensible heat content, removing sensible heat from the air by subjecting said air to an indirect heat exchange with water at -a lower temperature than said air, said water being maintained at said lower temperature by the continuous circulation of said water through a temperature reducing unit in which said water is brought into a heat exchange relation with the outdoor air, again passing said air over granular silica gel in a Water vapor adsorbing condition to further reduce the water vapor content of the air and at the same time increase its sensible heat content, then again removing sensible heat from the air by subjecting it to an indirect heat exchange with water maintained at a lower temperature than the air, said water being maintained at said lower temperature by continuously circulating it in the same manner as previously specified for the first-mentioned cooling water, then passing only a portion of the air through water sprays to reduce still further the sensible heat content of the air while increasing its content of water vapor and nally remixing said air portion of increased water content with air directly from said second-mentioned sensible heat removal step.

References Cited in the le of this patent UNITED STATES PATENTS 1,749,763 Flesher Mar. 11, 1930 1,762,762 Coiey June 10, 1930 1,872,783 Miller Aug. 23, 1932 

